This invention relates to an image formation system such as an electrophotographic image formation system or an electrophotographic printer for developing an electrostatic latent image on an image support in toner and in particular to an image formation system also serving as an MICR (magnetic ink character recognition) printer that can form images that can be read in MICR for forming a ferromagnetic toner image that can be magnetically read.
The image formation system of the invention can be used as a normal image formation system or an MICR printer.
In an MICR system which automatically reads a check on which symbols such as an issuance company name (for example, a bank name) are printed in ferromagnetic toner, automatically inputs the read contents into a computer, and displays the read contents on a display, an MICR font section printed on a check requires a proper quantity of magnetism, an accurate magnetic read symbol recognition capability, and durability to make an image hard to lose even in sliding friction with a magnetic head at the magnetism read time.
Thus, conventional checks have been prepared by offset print or with dot printers; in recent years, for example, MICR toner has been developed as proposed in the Unexamined Japanese Patent Application Publication Nos. Hei 4-358165 and Hei 7-3623 and electrophotographic check preparation is started.
To provide an MICR characteristic (magnetic read characteristic) and durability, the MICR toner uses special magnetic powder to stabilize the quantity of magnetism and contains a large amount of wax to stabilize the durability as compared with the normal toner used usually in an electrophotographic process. Thus, the image formation system using the MICR toner must be compatible with the electrophotographic process suitable for the MICR toner and therefore must become an MICR-dedicated printer.
The MICR printer is a check issuing machine and is used only in special fields of banks, etc., thus the distribution amount of the MICR printers on the market is extremely small and it is difficult to provide the MICR printer at a low price.
Hitherto, already existing printer parts have been used for most of the image formation system main unit and only special portions in the electrophotographic process suitable for the MICR toner have been changed for making the MICR printer fit for practical use at a low price.
However, the user requiring the MICR printer is also a user of a normal printer, of course; such a user needs to install both normal and MICR printers. Therefore, if the image formation system as the MICR printer can be provided at a reasonably low price, more than one image formation system becomes necessary and the required installation space and power consumption are increased accordingly; it is uneconomical.
Some users may use the MICR printer as a normal printer intact, but the distribution amount of the MICR printers on the market is extremely small as compared with that of normal printers as described above, thus the unit cost per print sheet becomes high.
Hitherto, an image formation system for forming toner images in different colors by changing a process cartridge having a black toner and a process cartridge having a color toner has been known as described in the Unexamined Japanese Patent Application Publication No. Hei 8-95468. However, an image formation system having both a normal image formation function using an electrophotographic process and a special MICR printer function is not yet known.
The inventors repeated experiments using process cartridges storing normal toner and those storing MICR toner in an image formation system comprising an image formation system main unit and a process cartridge mounted detachably in the image formation system main unit.
According to the experiments, the inventors have found the differences between the normal toner and MICR toner in the following three properties:
(1) Developing property PA0 (2) Cleaning property PA0 (3) Fixing property PA0 to provide an image formation system that can be used as an MICR printer by replacing a process cartridge in the image formation system comprising an image formation system main unit and a process cartridge mounted detachably in the image formation system main unit. PA0 an image support (51) formed on a surface with an electrostatic latent image; PA0 a cartridge mount space (V) for detachably mounting a process cartridge (U2) having a developing machine (66-69 and 71) having a developing roll (69) placed adjoining the image support (51) and transporting a developer to a developing area adjoining the image support (51) for developing a toner image on the electrostatic latent image on the image support (51); PA0 an optical writer (ROS) for forming an electrostatic latent image on the surface of the image support (51) by a light beam (L) of a predetermined light quantity; PA0 a transfer device (34) for transferring a toner image formed on the surface of the image support (51) to a transfer medium; PA0 a fuser (F) for fixing the toner image on the transfer medium at a predetermined fixing temperature; and PA0 a parameter change system (C+Me) having parameter storage means (Me) for storing image formation process parameters used when the process cartridge (U2) mounted in the cartridge mount space (V) is a normal cartridge and when the process cartridge (U2) is an MICR cartridge for forming a ferromagnetic toner image that can be magnetically read, the parameter change system (C+Me) for setting the image formation process parameters in response to the type of process cartridge mounted in the cartridge mount space (V). PA0 a developing machine (66-69 and 71) having a developing roll (69) placed adjoining the image support (51) and transporting a developer to a developing area adjoining the image support (51) for developing a toner image on the electrostatic latent image on the image support (51); and PA0 a detected member for cartridge discrimination (81) indicating that the process cartridge (U2) mounted in the cartridge mount space (V) is the MICR cartridge for forming a ferromagnetic toner image that can be magnetically read. PA0 the normal cartridge having a developing roll (69) formed with a molybdenum oxide film on a surface of an aluminum tube and the MICR cartridge having a developing roll (69) formed with an alumite film on a surface of an aluminum tube. PA0 if the process cartridge is the MICR cartridge, the parameter change system (C+Me) for changing the light quantity of the light beam (L) of the optical writer (ROS), one of the image formation process parameters, in comparison with the normal cartridge. PA0 if the process cartridge (U2) is the MICR cartridge, the parameter change system (C+Me) for changing a fixing temperature of the fuser (F), one of the image formation process parameters, in comparison with the normal cartridge. PA0 a parameter change input key, PA0 the parameter change system (C+Me) for setting the image formation process parameters in response to whether or not the parameter change input key is input. PA0 a cartridge discrimination unit (Sg) for determining whether the process cartridge (U2) mounted in the cartridge mount space (V) is a normal cartridge or an MICR cartridge for forming a ferromagnetic toner image that can be magnetically read, PA0 the parameter change system (C+Me) for setting the image formation process parameters in response to the type of process cartridge (U2) determined by the cartridge discrimination unit (Sg). PA0 the cartridge discrimination unit being made of an optical sensor for detecting a reflected light quantity from the mounted process cartridge (U2). PA0 the cartridge discrimination unit (Sg) being made of a magnetic sensor for detecting a magnetic force from the mounted process cartridge (U2). PA0 the cartridge discrimination unit having a cartridge contact terminal (103) coming in contact with either the mounted MICR cartridge or normal cartridge for outputting a different electric signal when the cartridge contact terminal (103) comes in contact with the either cartridge from an electric signal when the cartridge contact terminal does not come in contact with the either cartridge. PA0 a control panel having a cartridge discrimination input key, PA0 the cartridge discrimination unit being made of means for determining whether or not the cartridge discrimination input key is input. PA0 the detected member for cartridge discrimination (81) being made of a magnet. PA0 the detected member for cartridge discrimination (95) being made of a conductive member coming in contact with a component of the cartridge discrimination unit of the image formation system main unit (U1) for changing a detected potential of the cartridge discrimination unit.
The normal toner is easy to generate concentration, has an excellent cleaning property of unnecessary toner remaining on the surface of an image support 51, and requires a comparatively small heat quantity for providing stable fixing.
In contrast, the MICR toner is hard to generate concentration, has a poor cleaning property of unnecessary toner remaining on the surface of an image support 51, and requires a larger heat quantity for providing stable fixing than the normal toner.
The normal printer and the MICR printer also differ in required image quality. The normal printer, which covers all types of documents containing texts, drawings, illustrations, etc., requires high quality of solid black concentration, fine line reproductivity, halftone gradation, character section sharpness, etc.
On the other hand, the MICR printer needs quality of an image section made up of fine lines called MICR font. For appropriate magnetic signal strength of the MICR font section and accurate waveform recognition of magnetic signals proper to characters, fine line reproductivity and durability to make an image hard to lose even in sliding friction with a magnetic head at the magnetism read time are particularly required.
Therefore, the normal toner and the MICR toner differ in optimum parameters of image formation process.
If the (1) developing property difference and (2) cleaning property difference between the normal toner and the MICR toner can be absorbed in a process cartridge because a developing machine and a cleaner are placed in the process cartridge and if the (3) fixing property difference between the normal toner and the MICR toner can be absorbed in an image formation system main unit because a fuser is placed in the image formation system main unit, a normal cartridge and an MICR cartridge are provided as process cartridges and are simply replaced with each other, whereby an image formation system also serving as an MICR printer can be provided.
(Examination of Cleaning Property)
The inventors have found by experiment for the (2) cleaning property that if a urethane blade of high hardness that can clean the MICR toner harder to clean, the normal toner easy to clean can be cleaned. That is, the cleaning property difference between the normal toner and the MICR toner can be absorbed by using the cleaning blade for cleaning the MICR toner.
(Examination of Developing Property)
The developing property varies greatly in charge, exposure, and developing in image formation process; an infinite number of parameters exist such as potentials of charge bias, developing bias, etc., laser beam light quantity, image support surface material (photosensitive body) type, developing device configuration, developing roll material, form, magnetic pole density, and magnetic pole position, and the optimum values also change with combination.
Fundamentally, if a common combination and common optimum values of parameters to make the MICR toner and the normal toner compatible with each other are found, common process cartridge except for toner can be used, but the inventors cannot find them as a result of carrying out one experiment after another.
Then, assuming that parameters and optimum values can be changed only for replacement parts together with a toner storage vessel considering a price and common use, such as an image support, a charge roll, and a developing roll disposed in a process cartridge, the inventors repeated experiments. As a result, it has been found that an aluminum tube in the developing roll is formed on a surface with a molybdenum oxide film for a normal printer or an almite film for an MICR printer, whereby the MICR toner and the normal toner can be made compatible with each other.
The inventors have found that for use as an MICR printer, a change may be made to an appropriate laser beam light quantity conforming to the developing property of the cartridge to be used under the above-mentioned conditions.
(Examination of Fixing Property)
If the heat quantity given to toner is too large, an offset occurs; if the heat quantity given to toner is too small, a fixing failure occurs. Thus, usually a fuser of every image formation system has temperature measurement means and a heating source is controlled on and off according to one threshold value to keep the temperature constant. Since the heat quantity given to toner is the product of temperature and time, the optimum heat quantity difference between the normal toner and MICR toner at the fixing time can be adjusted according to the temperature or time. The inventors have found that if the same fixing time is applied to the normal toner and the MICR toner, it is necessary to raise the fixing temperature of the MICR toner because the MICR toner has a necessary fixing heat quantity larger than the normal toner.